Arabidopsis AIP1-2 restricted by WER-mediated patterning modulates planar polarity

Abstract

The coordination of cell polarity within the plane of the tissue layer (planar polarity) is crucial for the development of diverse multicellular organisms. Small Rac/Rho-family GTPases and the actin cytoskeleton contribute to planar polarity formation at sites of polarity establishment in animals and plants. Yet, upstream pathways coordinating planar polarity differ strikingly between kingdoms. In the root of Arabidopsis thaliana, a concentration gradient of the phytohormone auxin coordinates polar recruitment of Rho-of-plant (ROP) to sites of polar epidermal hair initiation. However, little is known about cytoskeletal components and interactions that contribute to this planar polarity or about their relation to the patterning machinery. Here, we show that ACTIN7 (ACT7) represents a main actin isoform required for planar polarity of root hair positioning, interacting with the negative modulator ACTIN-INTERACTING PROTEIN1-2 (AIP1-2). ACT7, AIP1-2 and their genetic interaction are required for coordinated planar polarity of ROP downstream of ethylene signalling. Strikingly, AIP1-2 displays hair cell file-enriched expression, restricted by WEREWOLF (WER)-dependent patterning and modified by ethylene and auxin action. Hence, our findings reveal AIP1-2, expressed under control of the WER-dependent patterning machinery and the ethylene signalling pathway, as a modulator of actin-mediated planar polarity.

TWISTED DWARF1 Mediates the Action of Auxin Transport Inhibitors on Actin Cytoskeleton Dynamics

“…Surprisingly, twd1-1 and both act7 alleles showed a striking apical shift in root hair positioning that was strongest in act7-4 twd1-1 and act7-4 act8-2 ( Figure 5B). Defects in planar root hair polarity have also been reported very recently for two new ACT7 alleles shown to influence ROP positioning (Kiefer et al, 2015). In analogy to epidermal twisting, root hair positioning was only mildly disturbed in act2-1 and act8-2.…”

“…pin2/eir1-4 (At5g57090; Luschnig et al, 1998);twd1-3 (Geisler et al, 2003); pin1-1 (At1g73590; Okada et al, 1991); abcb19-3 ( Lewis et al, 2007); abcb1-100 abcb19-3 (Wu et al, 2010); ABCB4:ABCB4-GFP (At2g47000; Cho et al, 2007), 35S:HA-TWD1 (Geisler et al, 2003), PIN1:PIN1-GFP and PIN2:PIN2-GFP (Abas et al, 2006); GFP-fABD2 (Sheahan et al, 2004); and DR5:GFP (Ottenschläger et al, 2003) were all in the Columbia wild type (Col-0). ABCB1:ABCB1-GFP, ABCB4:ABCB4-GFP, ABCB19:ABCB19-GFP, PIN1:PIN1-GFP, PIN2:PIN2-GFP, TWD1: TWD1-CFP, DR5 rev :GFP, and 35S:GFP-fABD2 transgenic lines were crossed into act7-4 or act7-6 (SALK_131610; Kiefer et al 2015), and isogenic, homozygous lines for the transgene in the F3 generations were used for further analyses. The same strategy was used for the act7-4 twd1-1 crossing.…”

A Framework for Lateral Membrane Trafficking and Polar Tethering of the PEN3 ATP-Binding Cassette Transporter

“…Mutants or marker lines employed in this study were provided by the corresponding authors of cited publications or obtained from the Nottingham Arabidopsis Stock Centre: act7-6 (N670149; Kiefer et al, 2015), act7-7 (N447790;…”

“…Mechanisms underlying PIN protein trafficking and targeting to specific domains have been addressed over the last two decades (Kleine-Vehn and Friml, 2008). Similarly, polar emergence of root hairs from a local area at the outer epidermal PM has been studied in detail (Grebe et al, 2002;Fischer et al, 2006;Ikeda et al, 2009;Kiefer et al, 2015). However, only more recently, proteins have become known that specifically localize broadly along the epidermal PM at the root surface facing the soil, termed the outer (lateral) membrane (Miwa et al, 2007;Strader and Bartel, 2009;Alassimone et al, 2010;Takano et al, 2010;Fendrych et al, 2013;Barberon et al, 2014).…”

ROP GTPases Structure-Function and Signaling Pathways

“…4). The accumulation of ROPs at future RH formation sites was found to be altered in the procuste1 cellulose synthase mutant, in clasp and sabre mutants that affect MT organization, and in actin7 and actin interacting protein1-2 mutants, suggesting involvement of the cell wall MTs and F-actin in the regulation of the RH initiation sites Pietra et al, 2013;Kiefer et al, 2015).…”